1. Field of the Invention
The present invention relates to a system and method for an auditory ear prosthesis. In particular, the present invention relates to the construction of a strut for connecting the medial surface of the stape footplate with the wall of the saccule.
2. Description of the Related Art
One type of conventional hearing aid provides for an air-conduction amplifying system such that a microphone picks up air conduction sounds, amplifies them and presents them in the ear canals as an air conduction signal to the eardrum. Such hearing aids offer a small frequency range as well as a small dynamic range of intensity.
Another type of conventional hearing aid is called a bone conduction hearing aid, which has been developed for users where the conventional air-conduction hearing aid is not satisfactory in improving hearing for those users. A bone conduction hearing aid is attached to the head of the user, and the output from a microphone pick-up is amplified and fed into a device which causes bone vibration. These devices operate over a small dynamic range and are designed principally for persons whose middle ears could not be surgically repaired or for very young children who have abnormalities of the middle ear that cannot be surgically repaired until they are older. As such, bone conduction hearing aids are rarely used.
Another type of conventional hearing aid involves implanting rare earth magnets in the temporal bone, and a microphone electronic coil system is used to cause the magnets to vibrate. The vibration of the magnets produces bone conduction hearing. These devices are also rarely used because of the surgery involved in drilling out the bone and installing the magnets therein.
Another type of hearing aid utilizes the supersonic frequency band, such as from 20,000 Hz and above, as disclosed in U.S. Pat. No. 4,982,434, which is incorporated in its entirety herein by reference. In such supersonic-frequency hearing aids, air conduction sounds in the audiometric range (from 100 Hz to about 10,000 Hz) are frequency-shifted to about 108 kHz or higher, and then these supersonic frequencies are transmitted by bone conduction or the like to the human sensory system. These signals are delivered by a bone conduction attachment, such as a high fidelity electrical to vibrator transducer, functionally connected for bone conduction in the head.
In U.S. Pat. No. 4,982,434, it was hypothesized that the supersonic hearing aid provides hearing to the user based on a system of hearing quite distinct from normal hearing based on air conduction. Instead, it uses bone conduction and parallels the primary hearing response of reptiles. In some reptiles, there is reduced air conduction hearing in reference to bone conduction. Hearing is mediated via both the cochlea and the saccule. In man, the saccule has been considered an organ responsible for balance and determining acceleration and movement. In reptiles, the saccule is a hearing instrument and it possesses hearing potential in amphibia and is the hearing organ of fish as well.
The evolution of the mammalian ear has spanned nearly 200 million years. Reptilian mammals responded to selective pressures and developed very sensitive air borne receivers with wide frequency ranges. The closest living relative to the common ancestor of these reptilian mammals are the extant turtles. While turtles hear a restricted range of frequencies, they preferentially process sound in the form of vibration. Turtles have at least two sensory receptors in their inner ears, the cochlea and the saccule. The cochlea is stimulated by bone conduction, which is different from the means of conduction in mammals. However, there also exists in turtles a physical connection between the wall of the saccule and the middle ear bone (stapes), with this physical connection not existing in mammals. Thus, when sound strikes the eardrum of a turtle, both the cochlea and the saccule are stimulated. In the case of a mammal, the saccule is isolated from direct contact with the stapes, and only very intense vibration of the stapes is translated to a corresponding vibration in the saccule.
The mammalian auditory system developed a sensitive receiver by evolving a thin, taught eardrum connected to a three-bone middle ear system that is capable of matching impedances between sound in air and vibration in inner ear fluid (perilymph). This ear development in sensitivity and in frequency range may have been detrimental to the saccule if it remained directly coupled to the middle ear. A very sensitive receiver may have exerted too much displacement on the saccule, hence overloading it. As such, it is hypothesized that the disarticulation of the saccule from the stapes may have been an adaptive mechanism for mammals.
The supersonic hearing aid as disclosed in U.S. Pat. No. 4,982,434 was believed to utilize direct bone transmission to the saccule, thereby enabling hearing to be maintained via a system independent of air conduction and the inner ear, although integrated with the air conduction system.
The supersonic hearing aid may not be suitable for every patient. Accordingly, there is a need to provide alternative approaches for saccule-mediated hearing.
It is an object of the present invention to provide a method and a system of inner ear activation through a prosthesis that connects the saccule to the stapes of a human ear.
The above-mentioned object and other advantages may be obtained by an auditory prosthesis system for a human inner ear that includes an eardrum, a saccule and a stapes. The system includes at least one strut that is disposed between the saccule and the stapes. Movement of the stapes is directed to the saccule by way of the at least one strut.
The above-mentioned object and other advantages also may be obtained by a method of implanting a hearing aid device into an inner ear of a human, the inner ear including a saccule and a stapes. The method includes a step of affixing one end of a strut to the stapes, wherein the strut has a hollow middle for receiving a material. The method also includes a step of applying the material into the hollow middle of the strut, thereby causing the other end of the strut to contact the saccule. Physical movement of the stapes caused by movement of an eardrum is directed to the saccule by way of the strut.
The above-mentioned object and other advantages also may be obtained by a method of implanting a prosthesis into an inner ear to enhance hearing. The method includes a step of providing a strut between a saccule and a stapes of the inner ear, thereby providing a direct contact between the saccule and the stapes. The strut provides direct stimulation of the saccule based on stimulation of the stapes.